For safety reasons, a ladder must be immobile when used, ie. when a user is on the ladder. However, it is also desirable that the ladder can be rendered mobile for the purpose of moving the ladder to another location.
A number of different solutions have been proposed in which some form of mobility means, such as wheels and castors, have been used, with the mobility means being movable between a retracted immobile position and a downwardly extended mobile position.
It is highly desirable that the mobility means return to the retracted immobile position as a default so that, in the absence of an applied mobilising force, the ladder is immobile.
A default-immobile ladder is disclosed in French Patent Publication 2,171,571. The ladder includes a rectangular frame carrying four wheels or castors. The frame can be urged downwardly in response to actuation of a lever thereby lifting the ladder and rendering the ladder mobile. The ladder returns under gravity to the immobile position when the lever is released, ie. the immobile position is the default.
The present invention aims to provide an improved default-immobile ladder.